Radio oscillation system



Oct. 25, 1932. F L LORD 1,884,011

RADIO OSCLLATION SYSTEM Original Filed Feb. l, 1926 2 Sheets-Sheet l lNvENToR MZK BY .Si A ORNEY,

Oct. 25, 1932. F. l.. LORD RADIO OSCILLATION SYSTEM Original Filed Feb. 1, 1926 2 Sheets-Sheet 2 ENToR l 55ML,

TORNEY.

Patented Oct. 25, 1932 Nr ariel:

FRANCIS L. LORD, OF NEWARK, NEW JERSEY RADIO OSCLLATION SYSTEM:

Application led February 1, 1926, Serial No. 85,294. Renewed July 9, 1932.

rlhis invention relates to improvements in radio oscillation systems.

Heretofore, it has been proposed to include in each so-called tuning stage of radio receiving systems a variable condenser and thereby tune eac-h stage by correlating the capacity of such variable condenser With the fixed induction of each stage and thus afford the tuning in of each stage by turning the rotor plates of the variable Condenser to the desired settings for the respective Wave lengths or frequencies. Such methods have been but partially successful, particularly in the socalled tuned radio frequency type of receiving sets, by reason of the inherent variation in the inductance and capacity values of the parts arising in the manufacture of the parts, the inherent variation in the assembly of the inductance and capacity affectingl parts of 20.' the respective tuning stages and further by reason of the variation in capacity valuesof the individual parts of each variable con denser. Further variations are introduced by the variations in the particular audion tubes Which' are installed originally and which may be replaced later in the respective tuning stages.

Such previous arrangements are furthermore unsatisfactory by reason of the employment of a variable condenser substantially as the sole frequency varying member or factor of each tuned stage, thereby necessitating the use of one or more coils in each tuning stage of a fixed inductance value or values, and giving rise to the practice in the commercial manufacture of radio receiving sets of acom promised77 or average inductance value, and thereby introducing an inductance in each timing stage which is incapable with the variations in capacity effected by the variable condenser of attaining optimum selectivity and substantial non-interference by radio oscillations other than that desired at the respective stages of setting of the variable condenser and by objectionable feed-back oscillations. Y

Pursuant to the present invention, the ininductance of the respective tuned stages if varied concomitantly With the capacity in attaining the respective settings of the variable condenser or other settable member of each tuning stage. Preferably, the variation in inducta-nce is attained by the use of a rotor coil such as a rotor coil in electrical series relation with a xed coil of a primary member of a radio frequency transformer, which rotor primary coil is in inductive relation to the coil of the secondary member as Well as in inductive relation to the fixed coil of the primary member of such transformer. Such arrangement of variable inductance by means of a primary rotor member may be attained by mounting the rotor primary coil on 4the shaft of the condenser as is set forth in my co-p'endin0r application Serial N o. 53,003, filed by me on August 28th, 1925 and entitled Mounting means for radio receiving sets, now U. S. Patent No. 1,640,200, granted August 28, 1927, wherein each rotor primary coil is mounted at approximately the angle of degrees to the axis of the shaft of its associated condenser, and provided with suitable means for adjusting the position and angular relation of any rotor primary coil relative to its associated fixed primary coil and fixed.y secondary coil, which are also mounted at approximately the angle of 45 degrees to the condenser shaft.

A further feature of the present invention is the` provision of suitable mounting means for such rotor primary coil to afford the positioningof the rotor primary coil to the axis of the condenser shaft at any desired angle varying from Zero as one limiting position to 45 degrees and greater if desired.

Another feature ofthe present invention is the employment of a rotor coil electrically connected in series with a fixed coil both of which coils are a part of the secondary member of a radio frequency transformer, the primary member being constituted of a fixed coil, which may be mounted in close inductive relation to the fixed coil of the secondary member and concentrically Within the same, the rotor secondary coil being brought into substantial concentricity with its associated fixed primary coil and the fixed secondary coil for a given position of the rotor plates of the condenser, say, when the rotor plates are in substantially complete common area relation with the stator plates, at which position the condenser is at its maximum capacity value.

Anotherv feature of the present invention @l is the employment of a rotor coil for each of 1the rotor secondary coil are jointly the primary and secondary members. In one form of regulating the inductance pursuant to my invention, the rotor primary coil and mounted l on va common bracket adjustable to and shaft, the aforesaid rotor primary coil and rotor secondary coil being in inductive relation to the fixed coil of the primary and the fixed coil of the secondary and the two primary coils and the two secondary coils in inductive relation to one another.

Further features and objects of the invention will be more fully understood from the following detail description and the accompanying drawings, in which Fig. 1 is a diagram showing` a circuit of any approved form tuned radio receiving set provided with an adjustable rotor primary coil and adjustable .fixed coil construction pursuant to my invention;

Fig. 2 is a perspective view of the assembly of a rotary variable condenser, an associated rotor coil of a radio frequency transformer mounted on the condenser shaft and the associated fixed primary coil and fixed secondary coil indicated in Fig. 1;

Fig. 2a is a detail horizontal sectional view of Fig. 2, showing the rear end plate of the condenser andthe angular relation of the rotor coil and the associated fixed coils in their respective positions indicated in Fig.

' 2, to wit;

Fig. 3 is a perspective view similar to Fi g. 2, but showing the rotor coil moved to its opposite limiting position, namely at the Stage of minimum capacity. value of the condenser;

Fig. 3a is a detail horizontal sectional view of the rear end plate of the condenser, the rotor coil and fixed primary and secondary coils in the positions of these parts indicated in Fig. 3;

Fig. 4 is a sectional elevation on line 5-5 of Fig. 3a;

Fig. 5 is a detail diagram of a circuit show ing a modification of the circuit of Fig. 1;

Fig. 6 is a perspective View showing the mounting jointly of a rotor primary coil and a rotor secondary coil on the shaft of their associated condenser;

' Fig. 6a is a horizontal sectional view of the rotor and fixed coils, their mounting means and of the condenser shaft, corresponding to Fig. 2; and

Fig. 7 is a detail horizontal sectional view' similar to Fig. 6a but illustrating separate assemblies of the primary rotor coil and the secondary rotor coil respectively relative to the fixed primary coil and the fixed secondary coil and the two primary coils and the two secondary coils in inductive relation with one another.

Referring to Fig. 1 of the drawings, the antenna is represented at 1, which is con nected by the aerial conductor 2 to the terminal 3 of the coil 4. The other terminal 5 of the coil 4 is connected by the lead G to the terminal 7 of the coil 8. The other terminal 9 of the coil 8 is connected by the conductor 10 through the junction point 11 to' ground 12. The coil 4 and the coil 8 constitute the primary member of the coupling 14; the secondary member in the form of a coil is indicated at 15. The coil 8 is preferably movably mounted, as in the form of a rotor coil and variable in setting as is indicated by the arrow The variable condenser 13 of the first radio frequency stage is preferably connected in parallel to the secondary coil 15 of the coupling 14. The terminal 17 of the secondary coil 15 is connected by the lead 18, lead 19 to the junction point 11 and to ground 12 and also by the conductor 2O to the negative terminal 21 of the A battery 22. The opposite terminal 23 of the secondary coil 15 is connected by the lead 24 to the grid electrode 25 of the audion tub@ 25 or equivalent. One terminal of the filamentelectrode 27 of the tube 26 is connected by the lead 28 to the negative terminal 21 of the A battery 22 and the opposite terminal of the filament electrode 27 is connected through the variable resistance 29 to the positive terminal 30 of the A battery 22. The plate electrode 31 of the audion tube 26 is connected by the lead 32 through the coil 33 ofthe primaryvmember of the coupling 34. The coil 35 of the primary of the coupling 34 is connected by the conductor 36 to the terminal 37 of the B battery 38. The primary coil 33 of the coupling 34 corresponds to the aforesaid rprimary coil 4 of the coupling 14 and the primary coil 35 of the coupling 34 corresponds to the aforesaid primary coil 8 of the coupling 14.

Vith present day audion tubes, in particular R. C. A. 201 A and De Forest D V-2 tubes, it is preferable to select the terminal 37 of the B battery 38 at 60 volts.

The negative terminal 39 of the B battery 38 is connected by the lead 40, lead 41 to the negative terminal 21 of the A battery 22 and therewith to the aforesaid parts connected to the negative terminal 21 of the A battery.

The secondary coil 42 of the coupling 34 is connected in the second radio frequency stage on its one side, similarly to the aforesaid secondary'coil 15 of the coupling 14, by the conductors 43, 41 to the negative terminal 21 of the A battery 22 and on its opposite side by A' nected in parallel to the secondary coil 39,

similarly as the variable condenser 13 in the first radio frequency stage. The filament electrode 48 of the audion tube 45 is connected n on its one side by the lead 49, lead 41 to the nega-tive terminal 21 of theA battery 22 and on its other side by the lead 50 through the variable resistance 51, lead 52 to the positive terminal 30 of the A battery rlhe plate electrode 53 of the audion tube 46 is connected through the lead 54 through the primary coil 55 of the coupling 56. The primary coil 55 corresponds to the aforesaid primary coils 33, 4 and is similarly connected with its rotor primary coil 57 corresponding to the' aforesaid rotor primary coils 35, 8. rihe rotor primary coil 57 is connected by the lead 58, lead 36 to the terminal 37 of the B battery 38.

The filament electrode 48 of the audion tube 46 is connected by its lead 49, lead 40 to the negative terminal 39 of the B battery 38.

The secondary coil 59 of the coupling 56 is connected on one side by the conductor 60, conductor 52, to the positive terminal 30 of the A battery 22 and on its opposite side by the conductor 61 to the grid electrode 62 of the audion tube 63 of the detector stage. The filament electrode 64 ofthe audion 63 is connected on one side by its conductor 65 to the conductor 66 leading to the negative terminal 21 of the A battery 22 and also to the negative terminal 29 of the B battery 38. The opposite side of the filament electrode 34 is connected through the variable resistance 66a to the positive terminal 30 of the A battery 22. The plate electrode 67 of the audion 63 is connected bythe lead 68 through the primary 69 of the audio transformer 70, thence by the lead 71 to the terminal 72 of the B battery 38. The terminal 72 is preferably at 45 volts.

The variable condenser Y 73 is connected preferably in parallel to the secondary Acoil 59 of the detector stage.

In attuning the aforesaid radio frequency stages and the detector stage, the variable condensers 13, 47, 73 are set for the desired frequency and the rotor coils 4, 33,55 are set for the highest emciency for the respec-A tive stages.

Preferably, the rotor coil 8 is mounted on the shaft of the variable condenser 13 and the number of turns of the rotor coil 8 is selected relative to the number of turns of its fixed primary coil 4 to correspond simultaneously and arcuately to the settings of thecondenser 13. In such arrangement, the primary rotor coil 8 is disposed concentrically Within the fixed primary coil 4 and the secondary coil 15, the fixed primary coil 4surrounding said secondary coil 15 and in close inductive relation.

In a similar manner, the primary rotor coil 35 is mounted on the shaft of the variable condenser 47 of the second tuned radio frequency stage and the rotor coil 57 similarly mounted on the shaft of the variable condenser 73 of the detector stage.

|The Vsecondar 74 of the audio transformer Y is connected on its one side to the grid electrode 75 of the audion 76 and at its opposite side to the lead 77 running to the conductor 78, conductor 66 to the negative terminal 39 of the B battery 38 and also through the conductor 41 to the negative terminal 21 of the A battery 22. The filament elect-rode 79 of the audion 76 is connected on one side by its conductor 80, con` ductor 78, conductor 41 to the negative terminal 21 of the A battery 22 and on its opposite side through the variable 'resistance 81 to the conductor 82 to the positive terminal 30 of the A battery 22.

The plate electrode 83 of the audion 76 is connected by the conductor 84 to one side of the primary coil 85 of the audio transformer 86, the opposite side of which coil 85 is connected by the conductor 87 to a positive terminal 88 of the B battery 38. rlhe terminal 88 under the circumstances mentioned hereinabove is preferably of volts. The secondary coil 89 of the audio transformer 86 is connected at one side to the grid electrode 90 of the audion tube 91 and at its opposite side by the conductors 92, 80, 7 8, 66 and 40 to the negative terminal 39 of the B battery 38 and jointly through the conductor 41 to negative terminal 21 of the A battery 22. The filament electrode 93 of the audion 91 is connected on one side by its conductor 94 to the negative terminal 21 of the A battery 22 and to the negative terminal 39 of the B battery 28 and on its opposite side by the conductor 95 through the variable resistance 96 to the positive terminal 30 of the A battery 22. The plate electrode 97 of the audion 91 is connected by the lead 98 to one terminal of the head phone 99, loud speaker or suitable sound emitting device. the opposite terminal of which is connected by the lead 100 to the terminal 88 of the B battery 38.

The formation of the coils of the primary of the radio couplings 14, 34, 56 may be as desired, but l prefer the formation of the windings and turns thereof as is set forth in my copending application Serial No. 2,520 entitled Reactance coils and filed by me in the U. S. Patent Office on the 15th day of January, 1925.

As indicated in the diagram of 1, the rotor coil of the primary andthe rotor plates of the associated condenser are mechanically coupled with one another and preferably of the type of coupling set forth in my aforelos iis

said Patent No. 1,640,200, and also set forth and claimed in my copendingapplication Serial No. 85,042 filed by me on January 30, 1926, and entitled Tuned radio frequency receiving system.

' In the aforesaid applications, the angle of the rotor coil relative to the shaft is predetermined, as for example, at 45 angular degrees. In my aforesaid patent No.y 1,640,200, the rotor coil is mounted on a bracket which provides for an adjustment clockwise or antlclockwise relative to the circular path of rotation of the rotor plates, to thereby adjust the position of the rotor coil for anyv given position of the rotor plates relative to the associated fixed primary coil and the associated fixed secondary coil.

In Figs. 2, 2a, 3, 3a and 4 in the present application, I provide for adjustable means for a rot-or coil such as the rotor coil forming part of the primary or rotor coil forming part of the secondary, whereby the angle 0f the rotor coil may be adjusted relative to the axis of the shaft of the condenser', as may be desired. For such purpose, the rotor coil is mounted on the shaft of the condenser at any desired angular relation with the associated fixed coils. As one form of such mounting, I employ, say, for the rotary variable condenser 47 of the circuit diagram shown in Fig. 1, an arm 120 of bakclite or the like for supporting the coil 35 at its opposite ends. The central portion of the strip 120 is provided with an openingl 121, see F ig. 4, for loosely receiving the body portion of the setting screw 122, the threaded end 1-3 of which is tapped in the threaded opening 124 of the extension arm 125 which is constructed to be secured to andV in axial alignment with the shaft 126, see Figs. 2 and 3, of the condenser 47. A suitable form of such connection with the condenser shaft is had by providing the recess 127 at one end of the extension arm 125 and the tightening screuT 128 for frictionally engaging the end portion of the condenser shaft 126 which extends rearwardly of the rear end plate 47a of the condenser 47. The opposite end 129 of the extension arm 125 is provided with the opening 130 through which the pig tails of the leads of the coil 35` are threaded and supported.

By untightening the setting screw 122, the supporting arm 120 of the rotor coil 35 may be set at any desired angle to the extension arm 125. Thus, as is indicated in Figs. 2 and 2a, the supporting arm 120 is set at an angle indicated by the dotted radial lines andthe arcuate double arrowed line 131, namely,.in this instance of say ten angular degrees.

The secondary coil, in this instance the coil 42 of the circuit of Fig. 1, and the fixed primary coil 33 are jointly mounted on the clamp member 132, which is adj ustably supported by the bracket 133, each of which may be of bakelite or the like. In this instance,

the fixed secondary coil 42 is disposed Vwithin the fixed primary coil 33.

The clamp member 132 may be forced of the base member 132a and the clamping element V1325 secured by the clamping screw 1320, such construction being of simplified form for the ready assembly and dis-assembly of the combined secondary coil 42 and iixed primary coil 33.

The clamping member 132is adjustably positioned on and supported by its bracket 133 by the provision of the tightening screw 134, passing through the opening 135 in the supporting bracket 133 and tapped in the threaded opening 136 in the base member 132a. The bracket 133 is secured to the rear end plate 47a of the condenser by means of its angled extension 137, which is provided with the opening 138 for receiving the securing screw 139 which is tapped in a suitable, threaded opening in the rear end plate 47a.

By unloosening the setting screw 134, the clamp member 132 may be set at any desired position relative to the bracket 133. In the instance indicated in Figs. 2 and 2a, the angle of the clamping member 132 relative to the bracket 133 is indicated by the dotted radial lines and double arrow arcuate line 140, which angle may be as desired and prefer'- ably is that of the angle 131. The bracket 133 is positioned substantially in alignment with the shaft 126 of the condenser 47.

Such relation of the parts of the respective adjustable mounting means for the rotor coil and the fixed coils of each radio frequency transformer for the one or more tuning stages, provides for the positioning of these coils in substantial concentricity with one another and with the axis ofthe condenser shaft when the rotor plates of the condenser are in any given settingr relative to the stator plates, as for example, when in complete common area relation with one another, at which stage the condenser is at its maximum capacity value.

The rotor plates of the condenser 47 are indicated at 141 and the stator plates 142. The dial of the condenser is indicated at 143. The usual reading of the dial 43 for such maximum capacity value of the condenser is c1007 In Fig. 3, the movable parts of the con` denser and the rotor coil have been rotated to substantially the minimum capacityvalue of the condenser, in which instance the reading of the dial 143 is O, at which stage the rotor plates 141 have been rotated substantially wholly out of common area relation with the stator plates 142. By such movement the coil 35 is osci'llated through the effective are indicated by the dotted radial and doubled arrowed arcuate lines 144 designated in Fig. 3a and indicated in perspective in Fig. 3. In attaining such arcuate displacement of an angle indicated by 144 or other angle determined by the settings of the ad- 'ill justable parts aforesaid, the coil by the rotation of the condenser shaft 126 is virtually rotated about an axis which passes through the screw 122.

A similar arrangement may be had for each rotor coil and its associated fixed primary and fixed secondary coils relative to their associated condenser in each of` the other timed stages, and the same or other angular relation of the adjustable parts thereof made relative to the condenser shaft.

In the vaforesaid arrangement as indicated in Figs. 2, 2a, 3, 3c and 4, upon timing the timing stages either of a single tuning stage type or two yor of three tuning stages, the last-named being indicated in Fig. 1, for any type Yof radio receiving system, the inductive reactance of each tuning stage is varied concomitantly with variation of its capacity reactance. For each rotor primary coil having a winding in the same direction as the winding of its associated secondary coil and its associated primary coil, the variation in inductive reactance is in the same direction as the variation of capacity effected by the turning of the rotor plates relative to the stator plates, assuming that each rotor coil `is in substantial concentricity with its associated secondary coil and its associated primary coil when the rotor plates are in substantially complete common area relation with the stator plates. Under such conditions, substantially no objectionable feed-back oscillations are transmitted from one timing stage to the other or to the remainder of the circuit of the radio receiving system for the various angular positions of the rotor coil and the corresponding angular positions of the xed Secondary and fixed primary coil for the range of angular position to the axis of the condenser shaft from a small angle, say five degrees to substantially degrees. `When the angle is increased above 45 degrees of any rotor coil and correspondingly of its fixed primary coil and vfixed secondary coil relatively to the condenser shaft, regenerative feedback oscillations are set up in the respective timed stages. f

However, l prefer to set the rotor primary coil at an angle less than 45 degrees and under present broadcasting conditions usually at the angle from 5 to 10 degrees relative to the associated condenser shaft, and the associated fixed secondary coil and the associated fixed primary coil at a similar angle.

Under such conditions of operation a maximum degree of selectivity is attained for the correlative positions at the respective timed settings a recurrent form of oscillation tuned to the desired frequency and yielding maximum volume under the control of the rheostat of the audion tubes of the tuned stages, with the elimination of all whistling and .ho'wling7 and other forms of objectionable feedback oscillations. Such optimum results are particularly attained when the grid condenser 111 which is connected on one side by the lead 61 to the negative -terminal 2l of the A battery 22 and to ground, as by means of the lead and conductor 41, whereby the grid element 62 of the detector tube 63 is constantly maintained at a negative value. rllhe grid leal: 110, as indicated in Fig. 1, is connected at one of its terminals to the terminal of the grid electrode and at its other terminal by the lead 110@ to the conductor 52 leading to the positive terminal 30 of the A battery 22.

lf desired, the rotor coil may be a part of the secondary member of the radio frequency transformer, the primary member being constituted solely of a fixed coil, in which instance such rotor secondary coil is mounted on the condenser shaft similar to the aforesaid mounting ofthe aforesaid rotor primary coil S5 set forth in Figs. 2 to 4. In the use of such rotor secondary coil, the angle of the same relative to the condenser shaft isl preferably of a greater magnitude, say,.from 35 to 45 degrees, for any of which positions vno objectionable feed-baclr oscillations are engendered in the radio receiving system.

rlhe most preferred form of my invention as applied to the use of a rotor secondary coil is in combination with a rotor primary coil as is indicated generally in the diagram of Fig. 5 and illustrated in two forms respectively in Fig. 6 and Fig. 7. In F ig."y 5, the rotor coil of the secondary 15 is designated 15a of the antenna or first radio frequency stage and the rotor coil of the secondary 42 is design ated 42a, and similar arrangement of the rotor coil is had for thesecondary 59, see Fig. 1; the remainder of the circuit of Fig. 5corresponds to that of Fig. l.

ln Fig. 6, the primary rotor coil35 and the secondary rotor coil 15a are jointly mounted on the strip 120 which is adj ustably mounted on a strip 120 similarly as in Figs. 2 to 4. In this instance, the rotor primary coil 35 is positioned outwardly of the rotor secondary coil 42a and the fixed primary coil 33 is positioned outwardly of the fixed secondary coil 42. Accordingly, upon rotating the dial 143 of the associated condenser 47, the rotor primary coil 35 and the rotor secondary coil 42a are jointly oscillated over an arcuate length of twice the angle at which the rotor primary coil and rotor secondary coil are set to the shaft 126 of the-associated condenser 47. The inner and outer relationship of positions of the respective rotor and fixed primary and secondary coils may be the opposite of that stated.

In Fig. 7, the rotor primary vcoil 35 is mounted individually on its supportingv arm 120 adjustably supported on the extension 125 of the condenser shaft 126 of the associated condenser 47 (not shown) and the rotor sec-j ondary coil 42a is similarly mounted on a sepa-ratearm 120@ for independent angular support on the extension 125.

Under present day conditions of broadcasting and reception, I prefer to set the rotor primary 35 at a lesser angle than that of the rotor secondary 42a, and to set the adjustable support 122 of fixed primary coil 33 at an angle substantially corresponding to that' of the rotor primary coil 35 and to set the similar adjustable support 132@ of the fixed secondary coil 42 at an angle substantially that of the rotor secondary coil 42a. The angular position of the rotor primary coil 35 is indicated by the arcuate line 131 and the angular position of the rotor secondary coil 42a by the arcuate line 131cv. Y

The set of primary coils 35, 33 are respectively in inductive relation to the set of secondary coils 42, 42a. Y

Preferably, the set of rotor secondary coil 42a and the fixed secondary coil 42 are positioned sufciently close to the metal rear end plate 47a of the condenser 4:7 to couple the same in inductive relation and the end plate 47a is connected to the negative terminals of the A battery 22 and of the B battery 38 and thence to ground for positive biasing ofthe secondary coils 42, 42a and for stabilizing effects and accordingly, the rotor plates of the condenser are pursuant to my aforesaid co-pending applications also connected to ground.

It will be observed that my aforesaid several forms of adjustable angular mounting for the rotor coil or rotor coils are in effect, gearing between the rotor coil or coils and the shaft of the associated condenser, which is positive inaction at all stages and in either direction and wholly without lost motion or back lash. f

The setting of theV aforesaid fixed primary coil and the fixed secondary coil for Vernier adjustment may be controlled from the front panel by a dial or the like, by mounting each clamp member 132 on a vertical shaft rotatively positionedthrough the opening in the bracket 133 and connecting such shaft by suitable worm gearing or the like to a shaft on which the dial or the like is mounted.

By forming the aforesaid primary rotor coil, or the aforesaid primary secondary coil, or both the rotor primary coil .and the rotor secondary coil, as the case may be of the construction of winding set forth in my application Serial No. 2,520, filed by me on January 15th, 1925 and entitled Reactance coil, the dimensions of the respective coils are materially reduced as compared with other forms of coil winding. Thus for the normal fixed coil serving as a primary or secondary of the aforesaid embodiments of my invention as an inner diameter of approximately 1% inchesV Y and the normal inner diameter of a rotor coil is approximately 071 of an inch. The width j of each coil is dependent upon the extent of capacity reactance desired to be imparted,

and generally the wider the coil, the less the value of the distributed capacity. Usually the width of the coil is from-less than 1/2 inch to one inch or less. Such advantages of reduced dimension of coil enables the respective rotor and relatively fixed coils to be positioned in close adjancency to one another when an inductive relation is desired and spaced from one another at a relatively short distance when a non-inductive relation is desired. Such advantage is of particular value to the manufacturer by reason of the decrease in dimension of the panels and of the cabinets.

From my observations, necessarily based on the broadcasting conditions existing at the present time, by selecting for the rotor primary coil the angle of from say 5 degrees to 10 degrees relative to the'axis of the shaft of its associated condenser and positioning the fixed coil of the primary at substantially the sameangle and disposing said primary coils to be substantially concentric with one another when the rotor plates of the associated condenser are in substantially complete common area relation with the stator plates, and by mounting the rotor secondary coil at a greater angle, say from 35 degrees to 45 degrees and the fixed secondary coil at substantially the same 35 degrees to 45 degrees and disposed concentrically with the rotor secondary coil when the rotor plates of the common associated condenser are in substantially complete common area relation with the stator plates, the highest degree of selectivity is attained for each of the positions of the condenser throughout its range of movement from its minimum reading toits maximum reading of capacity. VIn the operation of such form of my invention, it is my belief that the relatively lesser angular relation between the rotor primary coil and the condenser shaft as compared with the angular relation between the rotor secondary coil and the condenser shaft, is particularly effective in attaining sharp denition in the range of movement of the condenser' for the lower wave `length readings by reason of the rotor secondary coil being more remotely related in its inductive relation with the fixed primary coil and the rotor primary coil, effected by the wider angular displacement of the rotor secondary coil and thereby aifording the major control of the inductive reactance by the rotor primary coil. A similar sharpness of definition between the closely related wavelengths for the higher Wave length readings of the condenser by reason of the rotor secondary coil being oscillated through relatively larger arcuate displacements for the re- Yspective wave lengths, at which stages the rotor secondary coil plays the major role in the variation of the inductive reactance.

It will be understood, however, that the angles at which the rotor primary coil and the rotor secondary coil are mounted relatively to the associated condenser shaft may be varied and that the angle of the fixer primary coil and of the fixed secondary coil may also be varied at different angles respectively relative to the shaft of the associated condenser to attain a variable rate of variationfof the inductive reactance relative to the rate of variation of the capacity reactance as may be desired.

In any particular radio receiving set, the angular position of the rotor primary coil and of the rotor secondary coil for the respective stages are usually substantially uniform, excepting in the antenna circuit wherein the setting of the associated rotor primary coil and the rotor secondary coil is made in compensation of the capacity and induction values of the particular aerial with which such particular receiving set is equipped with. Preferably, the antenna circuit may be coupled wit the first radio frequency tuned circuit by the rotor coil for a primary or secondary as is indicated in the diagram of Fig. 2 of my copending application oerial No. 15,082, filed by me on March 12th, 1925, patented February 2, 1926, No. 1,571,900, and entitled Tuned radio frequency system, wherein such construction for a rotor primary coil is illustrated. A secondary rotor coil jointly with a primary rotor coil, of the form of coil construction shown in Fig.v 6 Aand 6a herein mav be employed, or as shown in Fig. 7 herein, such rotor coil, however, not being mounted on a shaft of a condenser, but set at a determined quiescent position for any particular antenna in compensation for its particular capacity inductance.

It will be observed that in the movement imparted by the condenser shaft to the rotor arimary coil or the rotor secondary coil, or both, as the case may be, the effective oscillatory setting of the rotor coil or coils varies the mutual inductance simultaneously and in the like direction of variation as the variation of capacity effected by the rotor plates relative to the stator plates and substantially commensurately therewith throughout the range of the setting movement of each tuning condenser and its coupled radio transformer.

Preferably, a single or common control or dial is arranged for the respective tuning condensers, thus affording a simplied tuning operation,particularly for amateur operators.

My invention in its above described -various forms is advantageous in radio receiving sets by reason of the substantially complete absence of distortion in the reproduction effected by the loud speaker or ear phones and also the absence of all howling and whistling, due to interference or objectionable feed-back oscillations.

Vhereas, I have described my invention by reference to specific forms thereof, it

will be understood that many changes and modifications may be made without departing from the spirit of the invention.

I claim:

1. In a multi-stage transformer coupled radio frequency system, each transformer comprising a relatively fixed primary coil, a

relatively fixed secondary coil, and a rel? atively movable coil connected electrically in series with one of said relatively fixed coils, means for mounting said relatively movable coil to rotate said coil at one position of its movement substantially coaXially with said relatively fixed primary coil, said relatively movable coil being throughout its range of movement in inductive relation with said relatively fixed coils, a tuning condenser for each radio frequency stage, and means for mounting and mechanically connecting the shafts of said tuning condensers respectively with said relativelymovable coils to attain an eective gearing ratio of two to one for effecting movement of said relatively movable coil to vary the total inductance between each relatively movable coil and its associated relatively fixed coils progressively increasingly in the same sense throughout the full range of such movement and progressively decreasingly in the same sense throughout the range of the reversed movement.

2. In a multi-stage transformer coupled radio frequency system, each transformer comprising a relatively fixed primary coil, a relatively fixed secondary coil, and a relatively movable coil connected electrically in series with one of said relatively lined coils, means for mounting said relatively movable coil to rotate said coil at one position of its movement substantially coaxially with said relatively lined primary coil, adjustable means for mounting said relatively fixed coils, said relatively movable coil being throughout its range of movement in inductive relation with said relatively fixed coils, a tuning condenser for each radio frequency stage, and means for mounting and mechanically connecting the shafts or said tuning condensers respectively with said relatively movable coils for effecting range of movement of said relatively movable coil to vary the total inductance between each relatively movable coil and its associated relatively fixed coils progressively increasingly in the same sense throughout the full range of such movement and progressively decreasingly in lthe same sense throughout the range of the reversed movement.

8. In a multi-stage transformer coupled radio frequency system, each transformer comprising a relatively fixed primary coil, a relatively fixed secondary coil, and a relatively movable coil connected electrically in series with one of said relatively fixed coils, means for mounting said relatively movable coil to rotate said coil at one position of its movement substantially coaxially with said relatively fixed primary coil, said relatively movable coil being throughout its range of movement in inductive relation with said relativelyiixed coils, a tuning condenser for each radio frequency stage, and rotary adjustable means for mounting and mechanically connecting the shafts of said tuning condensers respectively with said relatively movable coils for effecting range of movement of said relatively movable coil to vary the total'inductance between each relatively movable coil and its associated relatively fixed coils progressively increasingly in the same sense throughout the full range of such movement and progressively decreasingly in the same sense throughout the range of the reversed movement.

si. In a limiti-stage transformer coupled radio frequency system, each transformer comprising a relatively fixed primary coil, aY relatively fixed secondary coil, and a relatively movable coil connected in series with said relatively fixed secondary coil, means for mounting said relatively movable coil to rotate said coil at one position of its movement substantially coaxially with said relatively fixed primary coil, a tuning condenser for each radio frequency stage, and means for mounting and mechanically connecting the shafts of said tuning condensers respectively with said relatively movable coils for effecting range of movement of said relatively movable coil to vary the tota-l inductance between each relatively movable coil and its associated relatively fir-:ed coils progressively increasingly in the same sense throughout the full range of such movement and progressively decreasingly in the same sense throughout the range of the reversed movement.

5. In a multi-stage transformer coupled radio frequency system, each transformer comprising a relatively fixed primary coil, a relatively 4fixed secondary coil, and a relatively movable coil connected in series with Vsaid relatively fixed secondary coil, means for mounting said relatively movable coil to rotate said coil at one position of its movement substantially coaxially with said relatively fixed primary coil, a tuning condenser for each radio frequency stage, and mea-ns for mounting and mechanically connecting the shafts of said tuning condensers respectively with said relatively movable coils to att-ain an effective gearing ratio of two to one for effecting movement of said relatively movable coil to vary the total inductance between each relatively movable coil and its associated relatively fixed coils progressively increasingly in the same sense throughout the full range of such movement and progressively decreasingly in the same sense throughout the range of the reversed movement.

v6. In a multi-stage transformer coupled radio frequency system, each transformer comprising a relativelyv fixed primary coil, a relatively fixed secondary coil, and a relatively movable coil connected in series with said relatively fixed secondary coil, means for mounting said relatively movable coil to rotate said coil at one position yof its movement substantially coaxially with said relatively fixed primary coil, adjustable means for mounting said relatively fixed coils, said relatively movable coil being throughout its range of movement in inductive relation with said relatively fixed coils, a tuning condenser for each radio frequency stage, and means for mounting and mechanically connecting the shafts of said tuning condenser-s respectively with said relatively movable coils for effecting range of movement of said relatively movable coil to vary the total inductance between each relatively movable coil and its associated relatively fixed coils progressively increasingly in the same sense throughout the full range of such movement and progressively decreasingly in the same sense throughout the range of the reversed movement.

7. In a multi-stage transformer coupled radio frequency system, each transformer comprising a relatively fixed primary coil, a relatively fixed secondary coil, and a re1- atively movable coil connected in series with said relatively fixed secondary coil, means for mounting said relatively movable coil to rotate said coil at one position of its movement substantially coaxially with said relatively fixed primary coil, a. tuning condenser for each radio frequency stage, `and rotary adjustable means for mounting and mechanically connecting the shafts of said timing condensers respectively with said relatively movable coils for effecting range of movement of said relatively movable coil to vary the total inductance between each relatively movable coil and its associated relatively fixed coils progressively increasingly in the same sense throughout the full range of suoli movement and progressively decreasingly in the same sense throughout the range of the reversed movement.

In testimony whereof I have signed this specification this 30th day of January, 1926.

- FRANCIS L. LORD. 

